Paragon of Gathering Mists

Other blue creatures you control get +1/+1.
{U}, {T}: Another target blue creature you control gains flying until end of turn.

Clammy Prowler

Whenever this creature attacks, another target attacking creature can't be blocked this turn.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Altar of Dementia

Sacrifice a creature: Target player mills cards equal to the sacrificed creature's power.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice this artifact: Draw a card.

Copy Enchantment

You may have this enchantment enter as a copy of any enchantment on the battlefield.

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Fractured Sanity

Each opponent mills fourteen cards.
Cycling {1}{U} ({1}{U}, Discard this card: Draw a card.)
When you cycle this card, each opponent mills four cards.

Scatter to the Winds

Counter target spell.
Awaken 3—{4}{U}{U} (If you cast this spell for {4}{U}{U}, also put three +1/+1 counters on target land you control and it becomes a 0/0 Elemental creature with haste. It's still a land.)

Portal Mage

Flash
When this creature enters during the declare attackers step, you may reselect which player or permanent target attacking creature is attacking. (It can't attack its controller or their permanents.)

Skyline Cascade

This land enters tapped.
When this land enters, target creature an opponent controls doesn't untap during its controller's next untap step.
{T}: Add {U}.

Psychosis Crawler

Psychosis Crawler's power and toughness are each equal to the number of cards in your hand.
Whenever you draw a card, each opponent loses 1 life.

Zhalfirin Void

When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {C}.

Counterspell

Dramatic Reversal

Untap all nonland permanents you control.

Ledger Shredder

Flying
Whenever a player casts their second spell each turn, this creature connives. (Draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on this creature.)

Scourge of Fleets

When this creature enters, return each creature your opponents control with toughness X or less to its owner's hand, where X is the number of Islands you control.

Negate

Mind Sculpt

Gilded Lotus

Irenicus's Vile Duplication

Create a token that's a copy of target creature you control, except the token has flying and it isn't legendary.

Defiler of Dreams

Flying
As an additional cost to cast blue permanent spells, you may pay 2 life. Those spells cost {U} less to cast if you paid life this way. This effect reduces only the amount of blue mana you pay.
Whenever you cast a blue permanent spell, draw a card.

Broodbirth Viper

Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Whenever this creature deals combat damage to a player, you may draw a card.

Fraying Sanity

Enchant player
At the beginning of each end step, enchanted player mills X cards, where X is the number of cards put into their graveyard from anywhere this turn.

Aetherize

Return all attacking creatures to their owner's hand.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Talrand, Sky Summoner

Whenever you cast an instant or sorcery spell, create a 2/2 blue Drake creature token with flying.

Dream Fracture

Counter target spell. Its controller draws a card.
Draw a card.

Leyline of Anticipation

If this card is in your opening hand, you may begin the game with it on the battlefield.
You may cast spells as though they had flash.

Eluge, the Shoreless Sea

Eluge's power and toughness are each equal to the number of Islands you control.
Whenever Eluge enters or attacks, put a flood counter on target land. It's an Island in addition to its other types for as long as it has a flood counter on it.
The first instant or sorcery spell you cast each turn costs {U} (or {1}) less to cast for each land you control with a flood counter on it.

Tunnel Surveyor

When this creature enters, create a 1/1 white Glimmer enchantment creature token.

Murmuring Mystic

Whenever you cast an instant or sorcery spell, create a 1/1 blue Bird Illusion creature token with flying.

Trepanation Blade

Whenever equipped creature attacks, defending player reveals cards from the top of their library until they reveal a land card. The creature gets +1/+0 until end of turn for each card revealed this way. That player puts the revealed cards into their graveyard.
Equip {2}

Cut Your Losses

Casualty 2 (As you cast this spell, you may sacrifice a creature with power 2 or greater. When you do, copy this spell and you may choose a new target for the copy.)
Target player mills half their library, rounded down.

Disruption Protocol

As an additional cost to cast this spell, tap an untapped artifact you control or pay {1}.
Counter target spell.

Body of Knowledge

Body of Knowledge's power and toughness are each equal to the number of cards in your hand.
You have no maximum hand size.
Whenever this creature is dealt damage, draw that many cards.

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Blue Sun's Twilight

Gain control of target creature with mana value X or less. If X is 5 or more, create a token that's a copy of that creature.

Oneirophage

Flying
Whenever you draw a card, put a +1/+1 counter on this creature.

Crystal Grotto

When this land enters, scry 1.
{T}: Add {C}.
{1}, {T}: Add one mana of any color.

Glimmerburst

Draw two cards. Create a 1/1 white Glimmer enchantment creature token.

Torrential Gearhulk

Flash
When this creature enters, you may cast target instant card from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.

Island

Reality Shift

Exile target creature. Its controller manifests the top card of their library. (That player puts the top card of their library onto the battlefield face down as a 2/2 creature. If it's a creature card, it can be turned face up any time for its mana cost.)

The Grey Havens

When The Grey Havens enters, scry 1.
{T}: Add {C}.
{T}: Add one mana of any color among legendary creature cards in your graveyard.

Temple of the False God

{T}: Add {C}{C}. Activate only if you control five or more lands.

Sol Ring

Three Steps Ahead

Spree (Choose one or more additional costs.)
+ {1}{U} — Counter target spell.
+ {3} — Create a token that's a copy of target artifact or creature you control.
+ {2} — Draw two cards, then discard a card.

Rivendell

Rivendell enters tapped unless you control a legendary creature.
{T}: Add {U}.
{1}{U}, {T}: Scry 2. Activate only if you control a legendary creature.

The Mindskinner

The Mindskinner can't be blocked.
If a source you control would deal damage to an opponent, prevent that damage and each opponent mills that many cards.

Blackblade Reforged

Equipped creature gets +1/+1 for each land you control.
Equip legendary creature {3}
Equip {7}

Aboleth Spawn

Flash
Ward {2}
Probing Telepathy — Whenever a creature entering under an opponent's control causes a triggered ability of that creature to trigger, you may copy that ability. You may choose new targets for the copy.

Whispersilk Cloak

Equipped creature can't be blocked and has shroud. (It can't be the target of spells or abilities.)
Equip {2}

Wizards of Thay

Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Instant and sorcery spells you cast cost {1} less to cast.
You may cast sorcery spells as though they had flash.

Zellix, Sanity Flayer

Hive Mind — Whenever a player mills one or more creature cards, you create a 1/1 black Horror creature token.
{1}, {T}: Target player mills three cards.
Choose a Background (You can have a Background as a second commander.)

Psychic Corrosion

Whenever you draw a card, each opponent mills two cards.

Opal Palace

{T}: Add {C}.
{1}, {T}: Add one mana of any color in your commander's color identity. If you spend this mana to cast your commander, it enters with a number of additional +1/+1 counters on it equal to the number of times it's been cast from the command zone this game.

Denizen of the Deep

When this creature enters, return each other creature you control to its owner's hand.

Great Hall of the Citadel

{T}: Add {C}.
{1}, {T}: Add two mana in any combination of colors. Spend this mana only to cast legendary spells.

Tishana's Tidebinder

Flash
When this creature enters, counter up to one target activated or triggered ability. If an ability of an artifact, creature, or planeswalker is countered this way, that permanent loses all abilities for as long as this creature remains on the battlefield. (Mana abilities can't be targeted.)

Burnished Hart

{3}, Sacrifice this creature: Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Empress Galina

{U}{U}, {T}: Gain control of target legendary permanent. (This effect lasts indefinitely.)

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Crawlspace

No more than two creatures can attack you each combat.

Scrabbling Skullcrab

Eerie — Whenever an enchantment you control enters and whenever you fully unlock a Room, target player mills two cards. (They put the top two cards of their library into their graveyard.)

Graaz, Unstoppable Juggernaut

Juggernauts you control attack each combat if able.
Juggernauts you control can't be blocked by Walls.
Other creatures you control have base power and toughness 5/3 and are Juggernauts in addition to their other creature types.

Thought Vessel

Maelstrom Colossus

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Pristine Talisman

Bribery

Search target opponent's library for a creature card and put that card onto the battlefield under your control. Then that player shuffles.

Isochron Scepter

Imprint — When this artifact enters, you may exile an instant card with mana value 2 or less from your hand.
{2}, {T}: You may copy the exiled card. If you do, you may cast the copy without paying its mana cost.

Gigantoplasm

You may have this creature enter as a copy of any creature on the battlefield, except it has "{X}: This creature has base power and toughness X/X."

Archetype of Imagination

Creatures you control have flying.
Creatures your opponents control lose flying and can't have or gain flying.

Jace's Erasure

Whenever you draw a card, you may have target player mill a card.

Resculpt

Exile target artifact or creature. Its controller creates a 4/4 blue and red Elemental creature token.

Myriad Landscape

This land enters tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice this land: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.